Probability Quiz for IBPS

1. What is the probability that a card drawn at random from a pack of 52 cards is either a king or a spade?1) 17/52 2) 4/13 3) 3/13 4) 13/52 5) None of theseSolution:(2)Required probability =3/52 + 13/52 = 16/52 = 4/13(Note : why 13/52 because there are 13 spades and why 3/52 instead of 4/52 (there are fourkings)because one king is already counted in spades)

3. When two dice are rolled, what is the probability that the sum of the numbers appeared on them is11?1) 1/6 2) 1/18 3) 1/9 4) 1 5) none of the aboveSolution: (2) .n(S) =36n(E) = {(5,6),(6,5)} =2Therefore P(E) = n(E) / n(S) = 2/36 = 1/18

4. A basket contains three blue and four red balls. If three balls are drawn at random from the basket,what is the probability that all the three balls are either blue or red?1) 1 2) 1/7 3) 3/14 4) 3/28 5) None of the aboveSolution: (2)Probability to be a blue = 3 C3 / 7 C3 47Therefore Required Probability = 3C3 / 7C3 = 4 C3 / 7C3 = 5/35 = 1/7

5. A number is selected at random from the set { 1,2,3,…………………,50}. The probability that it is a prime, is1) 0.1 2) 0.2 3) 0.3 4) 0.7 5) None of the above
Solution:(3)n (S) =50Prime numbers are = 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47Therefore n(E)=15P(E) = 15/50 = 3/10 =0.3